1. Field of the Invention
The present invention relates to an initial voltage generation circuit and a method of generating an initial voltage, and particularly to an initial voltage generation circuit and a method of generating an initial voltage that can utilize an initial voltage level regulator to quickly regulate a voltage level of an inner reference voltage outputted by the initial voltage generation circuit.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating an initial voltage generation circuit 100 according to the prior art. The initial voltage generation circuit 100 includes a reference voltage generator 102, a reference voltage selector 104, and N stabilization capacitors C1-CN, where the reference voltage selector 104 includes N selection switch groups S1-SN and N switch control circuits SC1-SCN, and N is a positive integer. As shown in FIG. 1, the reference voltage generator 102 generates N reference voltage candidate groups, and each reference voltage candidate group corresponds to a selection switch group, where a selection switch group includes M parallel switches, and M is a positive integer. Then, each switch control circuit can generate a switch signal to control a selection switch group to output a reference voltage candidate of a reference voltage candidate group. For example, a first reference voltage candidate group VR11-VR1M of the N reference voltage candidate groups corresponds to the first selection switch group S1, where the first selection switch group S1 includes M parallel switches S11-S1M. Then, the switch control circuit SC1 can generate a switch signal SS1 to control the first selection switch group S1 to output a reference voltage candidate (e.g. a reference voltage candidate VR11) of the first reference voltage candidate group VR11-VR1M. In addition, the stabilization capacitor C1 is used for stabilizing the reference voltage candidate VR11.
Please refer to FIG. 2. FIG. 2 is a diagram illustrating variation of the reference voltage candidate VR11 within a period of time T. As shown in FIG. 1 and FIG. 2, because the reference voltage candidate VR11 needs to pass through the first selection switch group S1 before the reference voltage candidate VR11 is outputted, when the first selection switch group S1 outputs the reference voltage candidate VR11, the reference voltage candidate VR11 needs the period of time T to be increased to a target value VRT. Therefore, because the reference voltage candidate VR11 needs the period of time T to be increased to the target value VRT during power-up of a system, some circuits within the system may fail to power up. In addition, when the first selection switch group S1 is coupled to a large load, the large load may spend much time to power up because the reference voltage candidate VR11 needs a longer period of time to be increased to the target value VRT. Therefore, the initial voltage generation circuit 100 is not a good initial voltage generation circuit for the system.